First of all Crocodile is the first Shichibukai to be defeated by Luffy. He is the only one of the original Shichibukai to possess a Logia Devil Fruit. Crocodile is the first Logia-user that Luffy defeated.
In the Volume 63 SBS Oda drew the Shichibukai as children. Young Crocodile has almost exactly the same hairstyle as his adult self but is missing his trademark scar and hook. He is wearing simple clothing with a large pistol slung on his belt.
Miss Goldenweek’s Rainbow Color Trap reveals that his dream was to become the Pirate King.
It was noted that if the World Government had known Crocodile was head of Baroque Works, his bounty would be at least 
162,000,000.
Crocodile shares some similarities with Doflamingo:
- They are both former Shichibukai.
- They both are/were leaders of a powerful criminal organization with several Devil Fruit users.
- Crocodile was the main antagonist of the second saga of Part 1 (Baroque Works Saga), while Doflamingo was the main antagonist of the second saga of Part 2 (Pirate Alliance Saga).
- They both are Devil Fruit users and have mastered their powers to high levels and both are aware that Devil Fruit powers can be awakened (in fact Crocodile was the first character to mention the concept of a Devil Fruit being awakened when he explained the Jailer Beastswhere Awakened Zoan Devil Fruit users while Doflamingo is the first Awakened ParameciaDevil Fruit user to be shown).
- They both use coats as their common clothes.
- They both were present at Roger’s execution.
- They both aimed to control a whole country (with Doflamingo having succeeded).
- They both contrabanded illegal sustances (Dance Powder and SAD).
- Both characters’ defeats at the hands of Monkey D. Luffy seem to mirror each other:
- Luffy defeated Crocodile by blasting through Crocodile’s single attack with a barrage of punches, launching him through an underground cavern and into the air.
- Luffy defeated Doflamingo by countering a large group of Doflamingo’s attacks with one powerful punch, launching him through the air and into an underground cavern.
In the 5th Japanese Fan Poll, Crocodile is ranked the 15th most popular character in One Piece, making him the 2nd most popular of the original Shichibukai, the 3rd overall, and the most popular antagonist in the series. Coincidentally, 15 is the same spot he occupied in the first poll he was in.